A Spectroscopic Study of the Giant Low Surface Brightness Galaxy Malin 1

1 BlueMUSE Science workshop A spectroscopic study of the giant low surface brightness galaxy Malin 1 Junais Samuel Boissier Collaborators : Philippe Amram Benoit Epinat Alessandro Boselli Barry Madore Jin Koda Armando Gil de Paz J.C Muñoz-Mateos Laurent Chemin 10 November 2020 2 Low Surface Brightness Galaxies (LSBs) • Historical definition of LSBs based on disk central surface brightness (Freeman 1970): Bothun et al. (1997) 3 Low Surface Brightness Galaxies (LSBs) • Historical definition of LSBs based on disk central surface brightness (Freeman 1970): • LSBs may account up to 50% of all the galaxies in the universe (Impey & Bothun 1997, Martin et al. 2019) Bothun et al. (1997) 4 Low Surface Brightness Galaxies (LSBs) • In recent years, with powerful instruments (e.g. MUSE, Megacam, Dragonfly), there is a new interest in these sources. • LSBs also similar to galaxies with eXtended UV disk (XUV) (Thilker et al. 2007) • Ideal laboratories for the study of Star Formation activities in low density regime • Important to study this large population of galaxies • Their properties may redefine our knowledge of galaxy formation & evolution M83 with an XUV Disk 5 Low Surface Brightness Definitions • « Historical definition » (Freeman 1970) Diffuse galaxies Disk central surface brightness LSB • « Diffuse galaxies » (Sprayberry+1995) • « Ultra Diffuse Galaxies » (Koda+ 2015) UDG Hagen et al. (2016) 6 Low Surface Brightness Definitions • « Historical definition » (Freeman 1970) Diffuse galaxies Disk central surface brightness LSB • « Diffuse galaxies » (Sprayberry+1995) • « Ultra Diffuse Galaxies » (Koda+ 2015) UDG Malin 1 Hagen et al. (2016) MALIN 1 77 An extreme case of LSB !! Malin 1 image credits : NGVS u, g, i MALIN 1 88 Bothun et al. 1987 An extreme case of LSB !! MALIN 1 99 ~ 200 kpc diameter Bothun et al. 1987 An extreme case of LSB !! MALIN 1 10 ~ 200 kpc diameter M33 MilkyWay Bothun et al. 1987 An extreme case of LSB !! M83 11 A new spectroscopic study of Malin 1 Junais et al. 2020, A&A, 637, A21 Longslit data from Magellan – IMACS Spectrograph Observations in 2016 and 2019 4 slit positions => 2.5'' slit-width (2016); 1 slit position => 1'' slit-width (2019) 12 Extracted Spectra Hα • Spectrum extracted for 16 different regions of Malin 1 • Focussed on the Hα and [OII] emission lines => strongest of all [OII]3726,3729 • Measured quantities : ○ Wavelength shift (Hα and [OII] ) ○ Line Flux (Hα) 13 Extracted Spectra Hα • Spectrum extracted for 16 different regions of Malin 1 • Focussed on the Hα and [OII] emission lines => strongest of all [OII]3726,3729 • Measured quantities : ○ Wavelength shift (Hα and [OII] ) Rotational velocity SFR ○ Line Flux (Hα) 14 Malin 1 Hα Rotation Curve • First time to observe a steep rise in the rotation curve for Malin 1 up to ~400 km/s (inside ~10 kpc) • Created a new mass model based on the new rotation curve. • In the inner regions dynamics may be dominated by the stars (but our models couldn’t explain the highest velocities) • At large radii a massive dark matter halo remains necessary. • We need better quality data (e.g. IFU) 15 Star Formation Rate (SFR) Estimate • Estimated the local SFR surface density (ΣSFR) from the Hα line flux • Steep decrease in ΣSFR with radius similar to stellar profile • Inner region (< 1 Re) : consistent with an early type spiral (S0/Sa) • Outer region (> 1 Re) : similar to level found in XUV galaxies (The blue dashed line and shaded region indicates the typical ΣSFR level found in the disk of XUV galaxies; Bigiel+2010) Adopted effective radius of Malin 1 = 4 kpc Gonzalez et al. 2016, Bigiel et al. 2010 16 Work on Malin 1 : Conclusion ● Major result : Steep inner rise of Malin 1 rotation curve ● First SFR order of magnitude estimate for Malin 1 using Hα ● A better determination of dynamics and SFR of Malin 1 clearly requires large-IFU observations. ● Malin 1 was recently accepted for MUSE observation (PI-Gaspar Galaz, rank B observation in the cycle of 2021) ● With BlueMUSE, it would be possible to include most parts of the galaxy in a single pointing when four pointings are needed with MUSE. ● Similar study could be extended to other LSBs & XUVs in a broader context with Malin 1 as a prototype. 17 Need for BlueMUSE ● BlueMUSE will revolutionize the study of LSB universe ! ● Its larger FoV and high spectral resolution well suited for LSB observation ○ Reduce observing time ○ Known GLSBs and XUVs are in general ≳1 arcmin (Thilker+07, Boissier+08) ● Observe key emission/absorption lines that are of utmost importance to understand the nature and origin of these galaxies. ➔ Oxygen lines: ◆ Metallicity indication → Explain formation scenarios of GLSBs and XUVs ❏ Low metallicity → Large angular momentum disk (Boissier+2016) ❏ High metallicity → Head-on collision (Mapelli+2008) ➔ Hβ line: ○ Attenuation (Balmer ratio) → LSBs generally considered with low amount of dust (Hinz+07) ○ UV/Hβ ratio → Time delay between star forming events (Boselli+09) → Massive end slope of IMF (ratio of O stars to B stars; Koda+12) ○ SFR on short timescale (10 Myr) ● High resolution 2D kinematics → Dark Matter content → Effect of bars/asymmetries → Signs of accretion/gas removal (formation history) 18 THANK YOU 19 20 Extra slides 21 All Spectra 22 Central Spectrum 23 Mass Model 24 Proposed MUSE fields of Malin 1 White contours are from GALEX UV (Boissier+16) 25 Abundance Ratio • [N II]6584/Hα ratio --> Abundance estimator (Denicolo et al. 2002) • Observed high abundance at inner regions of Malin 1 • Could also be due to AGN activity • Boissier '16 model for Malin 1 predicts low abundance – only for outer disk • Need to make model for inner regions 26 Dust Attenuation • Hα/Hβ ratio --> Highly sensible to dust attenuation • Observed high Hα/Hβ ratio at inner regions of Malin 1 • Applied a standard Equivalent width correction for underlying stellar absorption. • Indicates low or no amount of dust in Malin 1 27 A new interest for Malin 1 & other giant LSBs • Deep optical images of Malin 1 reveal new features – Galaz et al. 2015 • The properties of the Malin 1 galaxy giant disk - Boissier et al. 2016 • Formation of a Malin 1 analogue in IllustrisTNG by stimulated accretion - Zhu et al. 2018 • GMRT HI study of giant low surface brightness galaxies – Mishra et al. 2016 • On the classification of UGC 1382 as a giant low surface brightness galaxy – Hagen et al. 2016 Galaz et al. 2015 • UGC 1378 : a Milky Way-sized galaxy embedded in a giant low-surface brightness disc – Saburova et al. Magellan Telescope g and r bands: 2019 • Spiral structure • Diffuse (tidal ?) regions • Massive Low Surface Brightness Galaxies in the EAGLE Simulation – Kulier et al. 2019 28 A new interest for Malin 1 & other giant LSBs • Deep optical images of Malin 1 reveal new features – Galaz et al. 2015 • The properties of the Malin 1 galaxy giant disk - Boissier et al. 2016 • Formation of a Malin 1 analogue in IllustrisTNG by stimulated accretion - Zhu et al. 2018 • GMRT HI study of giant low surface brightness galaxies – Mishra et al. 2016 • On the classification of UGC 1382 as a giant low surface brightness galaxy – Hagen et al. 2016 Boissier et al. 2016 • Surface brightness profiles of Malin 1 up • UGC 1378 : a Milky Way-sized galaxy embedded in a to 150 kpc in 6 photometric bands giant low-surface brightness disc – Saburova et al. 2019 • Massive Low Surface Brightness Galaxies in the EAGLE Simulation – Kulier et al. 2019 29 A new interest for Malin 1 & other giant LSBs • Deep optical images of Malin 1 reveal new features – Galaz et al. 2015 • The properties of the Malin 1 galaxy giant disk - Boissier et al. 2016 • Formation of a Malin 1 analogue in IllustrisTNG by stimulated accretion - Zhu et al. 2018 • GMRT HI study of giant low surface brightness galaxies – Mishra et al. 2016 • On the classification of UGC 1382 as a giant low surface brightness galaxy – Hagen et al. 2016 • UGC 1378 : a Milky Way-sized galaxy embedded in a giant low-surface brightness disc – Saburova et al. 2019 • Massive Low Surface Brightness Galaxies in the Boissier et al. 2016 EAGLE Simulation – Kulier et al. 2019 • Predictions for stellar mass, age, metallicity 30 A new interest for Malin 1 & other giant LSBs • Deep optical images of Malin 1 reveal new features – Galaz et al. 2015 • The properties of the Malin 1 galaxy giant disk - Boissier et al. 2016 • Formation of a Malin 1 analogue in IllustrisTNG by stimulated accretion - Zhu et al. 2018 • GMRT HI study of giant low surface brightness galaxies – Mishra et al. 2016 • On the classification of UGC 1382 as a giant low surface brightness galaxy – Hagen et al. 2016 • UGC 1378 : a Milky Way-sized galaxy embedded in a giant low-surface brightness disc – Saburova et al. 2019 • Massive Low Surface Brightness Galaxies in the EAGLE Simulation – Kulier et al. 2019 Zhu et al. 2018 31 IMACS Specifications 32 Emission Lines Hα Hβ 33 Absorption Lines Mg I (5175) Na I 34 Existing Models 35 Malin 1 surface brightness profile Data Source : Lelli et al. 2010.

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